A study of teenagers' sleep habits revealed that mean number of hours slept per night was 7 hours, with a standard deviation of 1.5 hours. Assume that the data are normally distributed. a. What is the probability that a randomly selected teenager sleeps more than 8.5 hours per night? Explain.

b. What is the probability that a randomly selected teenager sleeps less than 4 hours per night? Explain.

c. The national Sleep Foundation recommends that teenagers get between 8 and 10 hours of sleep per night. Estimate the probability that a randomly selected teenager gets between 8 and 10 hours of sleep. Explain.